Vehicular interior trim parts are typically manufactured with an exterior decorative skin layer that is backed with a layer of foam, and in particular, polyurethane type foam. The skin material may be a thermoplastic elastomer (TPE) type material. The bond between the foam layer and the skin layer may be capable of enduring environmental temperature extremes, including large changes in temperature over a relatively short period of time.
There are two modes of failure of the bond between the skin layer and the underlying foam: (1) adhesive failure which occurs when there is a separation of the skin layer from the underlying foam; and (2) cohesive failure which occurs when the failure of the foam is observed. As the skin layer is removed, a residue of the foam on the skin layer may remain, indicative of the failure of the foam. As vehicle lifetimes extend over numerous years, there remains a growing need to improve the bonding between the underlying foam layer and the skin layer.